Toll metering by discriminating selector repeaters



Jan. 4, 1949. R. TAYLOR ErAL TOLL METERING BY DISCRIMINATING SELECTOR REPEATERS Filed Deo. 11, 1944 6 Sheets-Sheet l lNvENToRS REGINALD TAYLOR GEORGE THOMAS BAKER ATTORNEY Jan. 4, 1949. y R. TAYLOR ETAL 2,457,945

. TOLL METERING BY DISCRIMINATING SELECTOR REPEATERS Filed De'o. 11, 1944 1 e sheets-sheet 2 LZ LMF INVENTORS REGINALD TAYLOR GEORGE THOMAS BAKER ATTORNEYA 6 Sheets-Sheet 5 LSW R. TAYLOR ETAL LZ LH OAS l LSC LMF l DA3 25172 TOLL METERING BY DISCRIMINATING `SELECTOR REPEATERS Jan. 4, 1949.

Fiied Dec. 11, 1944 LLD TA TB TC TDTET INVENTORS' .REGINALO TAYLOR GEORGE THOMAS BAKER w@ "ATTORNEY 4.111,4, 1949'. i RTAYLORIETAL," 2,457,946

TOLL METERING BY DISCRIMINATQING SELECTOR -REPEATERS Filed Dec. 11. .1944 e shees-sheet`4 I i r .i 2122 3242526 2728 ZSO lo 9 8 7 6 5 4 3 21 l AB INVENTORS REGINALD TAY LOR GEORGE THOMAS 'BAKER ATTORNEY Jam. 4, 1949.

Filed nec. 11, 1944 G'Sheets-Sheet 5 REGINALD TAYLOR GEORGE THOMAS BAKER ATTORN EY Jan. 4, 1949.` R. TAYLOR ErAL 2,457,946

Y TOLL HETERING BY DISCRIMINATING SELECTOR REPEATERS Filed Dec. 11, 1944 sheets-sheet e INALD TAYLOR ESRGE THOMAS BAKER ATToRNg-Y Patented Jan. 4, 1.949

TOLL METERING BY DISCRIMINATING SELECTOR REPEATERS Reginald Taylor and George Thomas Baker, Liverpool, England, assignors to Automatic- Electric Laboratories Inc., Chicago, Ill., a corporation of Delaware Application December 11 1944,Seral No. 567,552 In Great Britain February 16, 1944 The present invention relates to telephone systems and automatic switches for use therein and On such netwo-rks it is usually considered de- I sirable that all calls for which registration against a calling party can be effected on either a single or a multi-fee basis shall be completed automatically and the presentinvention is chiefly concerned with the metering arrangements for such calls at satellite exchanges.

rI'w-o methods are disclosed in an article entitled Multi-Fee Call Dialling and Registration in the Post Onice Electrical Engineers Journal, Volume 31, page 5. According to one of these methods multi-fee metering equipments are provided which are accessible from satellite exchange D. S. R.s of standard type over the Wipers and banks of hunter switches, while in the other method combined multi-fee metering equipments and digit discriminating equipments are provided which are accessible from satellite exchange first numerical selectors over hunter switches, the

D. S. Hfs thus being replaced by first selectors which are of slightly modied form to cater for impulse repetition to the main exchange. In both instances the satellite exchange multi-fee metering equipments are taken into use on every type fof originated call regardless of whether a single or multi-fee meter registration will be required. Hence the number of metering equipments required to give the requisite grade of service is more than strictly necessary. Thechief object of the invention is to provide a simple 2 mentfor controlling multi-fee metering is arranged to be accessible over the wipers of a discriminating selector repeater.

A further feature of the invention is that in a telephone system including satellite exchanges equipped with discriminating selector repeaters over which local calls are completed after the absorption vof one or more digits, equipment arranged `to control the operation of a discriminating selector repeater in accordance with the extent of its setting is arranged also to control the transmission of a distinctive signal to the calling party and the release of the partially set up connection if an unassigned number is dialled.

The invention will be better understood from the following description of one method of carrying it into effect, reference being had to the `accompanying drawings comprising Figs. 1-8.

` Figs. 1 and 2 show the circuit of the selector arrangement whereby greater economy in the use of multi-fee metering equipments is obtained without any appreciable complications in other directions.

According to one feature of the invention, in

a telephone system including satellite exchanges 5' equipped with discriminating selector repeaters over which local calls are completed after the absorption of one or more digits, impulse responding equipment associated with a discriminating selector repeater is arranged to control the taking into use of equipment for controlling multi-fee metering in such manner that a setfof multi-fee metering equipment is only taken into use after the value of the impulses receivedhas repeater portion of a D. S. R. while Figs. 3 and 4 showcircuits of the discriminating relay portions `adapted respectively to absorb the first and second digits and discriminate on the rst, second and third, and to absorb the rst digit and to discriminate on the first and second digits. Either set of discriminating relays can be associated4 with theI selector repeater portion according to the Y requirements of the network concerned. The selector mechanism .is assumed to be of the two-magnet vertical and rotary type such as is disclosed in Patent No. 2,028,689 granted January 21, 1936,` to Saxby.

Fig. 5 shows a trunking diagram of a typical satelliteexchange area. The numbering scheme for this area involves absorption of first and second digits and discriminationion first, second and third digits, hence the discriminating relays of Fig. 3 will require to be used on the D. S. R. The precise numbering arrangements which are taken by way of example are catered for by the particular cross-connections shown between the discriminating relays and the selector vertical bank.

Fig. 6 tabulates the absorbing and discriminating facilities required on the first, second and third digits of numbers in the above-mentioned scheme.

`the various cross-connection terminals TA-TK and TT-TZ of Fig. 3, an asterisk indicating that the available facility can be decided at will. Fig.

single or multiple meter fees according to the location of the wanted exchange with respect to the calling exchange. The fee determination on such calls is effected by multi-metering equip ments which are located in common groups accessible via a particular level of the satellite ex` change D. S. R.s, and comprising digit storing uniselectors by means of which the appropriate fees for giving dialled numbers can be ascertained,

Referring now to Figs. l and 2 and considering the circuit operation, on the seizure of the D. S. R. by a calling satellite exchange subscriber either via a line finder or by his uniselector, relay A is operated over the loop and operates relay B by way of contacts N3, MDB and AI. Relay JG is also operated by way of contacts N3, MD3, AI and N4. Relay B thereupon earths the P conductor at contacts BI, completes a locking circuit for itself and relay JG at contacts B5, and at contacts B6 lights the supervisory lamp LP, the circuit of which extends to battery over lead I by way of a delayed alarm. Relay JG at contacts JGI energises relay MD, at contacts JGZ prepares the circuit of the vertical magnet VM, at contacts JG3 connects the junction hunter magnet JHM to the test wiper JH4 of the junction hunter, at contacts J G5 prepares for the connec tion of dial tone to the calling party by way of the left-hand winding of relay I, at contacts J G6 prepares a locking circuit for itself and at contacts JG? opens the connection between the last Contact in the bank JH4 and lead I4 which extends to an overflow meter. Relay MD operates at this time and prepares a locking circuit for itself at contacts MDI, at contacts MDZ prepares the release circuit of the D. S. R., at contacts M133 prepares a circuit for relay C which is at present short-circuited, :at contacts M134 connects an additional earth to the P conductor, at contacts MD5 connects earth to the left-hand terminal of relay K and at contacts MDG prepares an impulsing circuit over the positive wiper of the D. S. R.

The junction hunter switch follows usual prace tice in that, although it is of the homing type, the wipers are normally resting on the first junction of the group. The twenty-fifth position of the bank does not connect with any junction however, this position being set aside for returning a busy tone to the calling party in case all junctions should be engaged; hence twenty-four outlets, Which may be graded, are available to the junction hunter wipers,

On the connection of the switch magnet JHM to the test wiper JI-III, the switch commences hunting to nd a free junction. When this is encountered, relay K is no longer short-circuited by earth picked up by wiper JH4 and energises in series with the magnet which cannot now operate. Relay K thereupon at contacts KI completes the dial tone circuit, at contacts K2 completes a locking circuit for itself, at contacts K3 earths the test wiper to busy the seized outlet, at contacts K4 opens a point in the homing circuit of the switch, at contacts K5 and K6 loops relays D and I across the outgoing junction, at contacts `K'I opens a point in one circuit for relay SC and at contacts K8 opens a point in the circuit of the D. S. R. rotary magnet RM which circuit extends to earth over lead I6 by way of delayed alarm equipment. Relay I now operates and completes the locking circuit of relay MD while relay D which is polarised by the rectiers MRB and MRC is unable to operate under these conditions.

contacts B5, AI and JGZ,

In case all the junctions of the group are busy, the switch Wipers are brought to rest in the last position owing to the absence of earth on the 25th contact and relay K operates as before. Dial tone is now returned to the calling party in order to enable local or other non-junction calls to be completed and busy tone is substituted later if the call proves to be for the main exchange.

The calling party now dials the first digit and relay A follows the impulses in well-known manner. Each time it releases, a circuit is completed for the vertical magnet from earth by Way of Relay B is intermittently short-circuited during the train of impulses but not for sufficiently long to cause its release. Magnet VM receives a corresponding number of impulses and the switch wipers are raised to the desired level. At the same time impulses are repeated at contacts A2 over the junction to the main exchange to operate the distant incoming selector. On the iirst release of relay A, relay C is no longer short-circuited and operates. Thereupon at contactsCI it energises relay CR and at contacts C2 closes a circuit in series with contacts B2 for short-circuiting relays D and I in order to give a low impedance impulse-repeating loop. Relay CR at contacts CRI closes another point in the alternative circuit for relay SC, at contacts `CR2 prepares a circuit which will be effective subsequently for reintroducing relays D and I into the outgoing loop in two stages, at contacts CR3 energises relay J, at contacts CRA closes a further holding circuit for relay K, at contacts CR5 prepares for the connection of earth over lead LSW and at contacts CR5 closes an additional holding circuitfor relay JG. Relay J at contacts J I prepares the metering.v circuit, at contacts J2 disconnects dial tone, at contacts J3 prepares a locking circuit for itself, at contacts J4 prepares a locking circuit for relay RS and at contacts J5 disconnects the supervisory lamp LP and closes a multiple locking circuit for relay MD.

On the 'rst vertical step of the switch the offnormal contacts are operated and at contacts N4 the initial circuit for relay JG is opened and it remains held over its right-hand winding and contacts JGIi.l Relay C is also intermittently short-circuited during the train of impulses but remains held until the end of the train. Relay C then releases and opens the circuit of relay CR but the latter relay is slow to release due to its slug and while it holds up, earth is connected to conductor LSW. Meanwhile at the end of the first impulse train the main exchange incoming selector will proceed to cut into the level dialled and to hunt in the rotary direction for either a subsequent selector in the main exchange or an outgoing auto-to-auto relay set giving access to another exchange.

vAt this point in the description consideration will be given to the network numbering scheme which is assumed to be as follows:

Routed to manual board via D. S. R. Level 0 O v l. 100G-6999 Routed to Main Single Fee r {9000 9999 Routed through Main Multi-fee 8000-8999 Routed through Main to other 174000-74999 sateuites 175000-75999 71400-71799 Local numbers {7200U-72099 72599-72999 Routed to adjacent satellite via D. S. R. Level 3 '73000-73999 If the first digit of a single fee main exchange number such as 16 or 9 is dialled, the application of earth to signalling lead LSW will be without effect on the associated discriminating relays and no'return earth potential will beextended back fromthese relays toany of the other signalling leads, a main exchange callbeing char-` cal magnet at contacts 1J G2, and at contacts JCi` connects up abusy tone circuit so that if the junction-hunter JH has been driven to the twenty-ilfth position, busy tone over lead i3 is applied to lthe'left-hand winding of relay I and transmitted by induction to the calling `subscriber. In this case since there is no circuit for relay VI, relays MD` andiJ now release in turn and relays A, B and K fall away when thecalling party hangs up. l v

`Assuming however that a main exchange Junction has been seized, relays A, B, MD and J remain` energised and subsequent digits produce corresponding operation'of relay A whichat contacts A2 repeats the digits to the main exchange to set up the selectors therein to effect connection with the wanted main exchange party. When the called subscriber answers, relay D operates owing to the reversal of currentiiow over the loop and at contacts `DI preparesa circuit which will not be eiiective in the present instance andat contacts D2 releases relay MD. Relay MD opens the circuit for relay J and during the slow release period of this latter relay earth is applied to the meter lead M by way of contacts MD5, J l, RSZ and MDS. Relay MD also at icontacts MDZ prepares the restoring circuit for the rotary magnet RM of the D. S. R.

When the calling party hangs of the conversation, relay A releases and at contacts AI short-circuits relay B `for sufficiently long to cause its release while` at contactsAZ `it opens the outgoing loop so as to initiate release of the main vexchange selector train. During the release of relay B, relay C operates and again brings up relay CR which at contacts CR4 main-4 ing earth is removed from the junction hunter test wiper, the usual junction i guarding relays serving to ensure that the junction remains guarded for a further period` suilicient to cover the release of the main exchange switches. At contacts K2 guarding earth is reapplied to the incoming P Iconductor by way of contactsV N2, K2, LDS and SC4 until the DLS. R.has released, While at contacts K8 a self-interrupting circuit is cornpleted for the rotary magnet RM. The wipers are accordingly rotated clear of the banks after which they fall and rotate back under the banks by spring tension to their normal position where the off-normal contacts `are restored. At contacts Nl the circuit of the rotary magnet is then opened while contacts N2 remove the guarding earth from the incoming P conductor and the equipment is then completely restored to normal.

If the call has been to an operator in the main exchange, metering will not normally be effected, that is to say therewill be no reversal to operate relay D, but instead `battery will be connectedto `up atthe end thepositive conductor to give an` operator hold facility. `This produces no effect until the calling party hangs up whereupon relays A andBrelease in turn and relays C and CR are momentarily operated.A On the release of relay B, the circuit of relay J is openedand a circuit is completed for relay I tothe battery connection atthe operatorfs" position. yRelay `I maintains relay MD which preventsthe release of the D. S. R. until theoperator takes down the connection.` When this occurs, relaysI, `MD and K release, the junctionhunter JH homes and earth is removed from the P lead at contacts MD4. J i ,n

Assuming nowthat the rstdigit dialled is "7, in every case absorptiontwill be required at the satellite exchange. .The operations which take place responsive tothe seizure of the D. S. R. are the same as previously described up to the end of theiirst impulse train, at which time relays yA,B;`

JG, l\/ID,J` and `Klare operated, relay C has just releasedV and relay CR is being held `by its slug.

In this case since the digit dialled is 7, `the appli-iy cation .of earth to lead LSWwill result in the operation of relay DA if `the, discriminating,` relay group is connected as shown in Fig. 3. The vari-1 ous possibilitiesofithis scheme `of connections will be dealt ,within detail later and at this timeA it will merely be pointed; out that .the operation of relay DA. results in the connection of earth to lead LH and also to lead LZ. The earth on lead LHserVes tomaintain relay 'JG over its righthand winding` while the earth on lead LZ is extended` over contacts MD2, H4, RMC andNl to rotary magnet RMto restorethe D.` S. R. to nor,-`

energising circuit sothat earth ismaintained` on f lead LH to keep relay DA locked up.

Iflthe second digit `dialled is 3, which with trie assumed numbering scheme denotes a call to the adJacent satellite exchange, the D.` S. R. wipers are raised to the'third level and earth is` then` applied ,to lead LSW during the release time of,`

relay CR. With the conditions nowpreuailing in the discriminating relay group, Fig. 3, this earth-,extends to lead LLD and eects the operationof relayLD. This relay at contacts LDI energises relays RS and H, at contacts VLD2` and LDS connects up the line Wipers of the DQS. R.,

at contacts LDB prepares the metering circuit,` at contacts LDSopens the loop over the junction in vorder to release the main exchange switches and at contacts LDB completes a locking circuit for itselfand renders `relay K dependent upon relay CR so that Whenthis latter relay :finally` relay SC,'`at contacts RS4 completes a circuit for the upper windingof` relay H, at contacts RS5 preparesan alternative circuit for the lower winding of relay-H, 1at contacts RSG closesa point in the metering circuit which will not be effective.- in-..the1 present caseA and; at. mantacts:` RST opens) a point in the releasel circuit for thee D. S. R. Relay H- at contacts II|- and H3 d-iscon nects. theline wipers:- of` the D; S. R. to prevent; interference during the hunting operation ,at contacts H2 connectsA itsv own lo\vert,winding; to*v the test wiper l? and. at contacts H42 completes a self-interrupting; circuit for: the rotary,A magnet RMirom. earth'. overf contacts. LDI. .The switch. therefore. now Vcommences: to huntI over the; selected third level. and it` will bes seen. thatrat; each. operation. of. the. rnagnetrthey interrunter. springs RMC are opened and. hence. the; circuit iorv the; upper winding. of relay H. is; interrupted. It busy lines are: encounteredhowever, the test` wiper picks. up' earth. to maintainl relay I-I by` way-A ofi its lower winding. The initial ycircuit for thisv winding is opened at contacts NRt' on the iirst rotarystep of the switch. Accordingly the switchcontinues to step until a, free` line is encountered or the wipers are driven to the eleventh position. In the latter event the cam springs areoperated and atcontacts Si `an overiiow meter is operated? by'way of lead l1, at contacts S2 busy tone from common lead H is sent back to the calling party' and' at contacts Si relaySC is operated.' 'fi-hei calling party is thus advised thatY he cannot obtain his connection and when he hangs' up; release takes place inv the manner previouslyl described. f If' a freeoutlet isl found, the test wiperfailsj to encounter earth and relay H` releases' quickly when the interruptor contacts open, thereupon maintaining the circuit of magnet RM operi at contacts I-I4` and applying guardingl earth to ther P wiper over contacts I-I-Z; 'Ihe'repeaterl element` is now connected to an incoming thirdK selector at the adjacent satellite exchange;` thefD; SKR. having functioned asa second selector. I, i

WhenV the remainingv digits of 'therequirecf number are received, relay A again responds' and" serves merely tok repeat these digits to the ad-4 jacent satellite exchange selectors to eiect connection with thev wanted party therein. Ylli/"hen this party repliesrelayD'- is operated; in thfejusua-l" mannen and releases relay MDso that during the slow release time of relay' J, aI metering impulse is tran'srnittedy overL conductor by way of coni-y tacts MD5?, Ji and LD`4- Duringy the conversa-f tion', relays Bi, LD; RISE, I-`and*Dreniairroperate@4 inthe-msn. f p j VWhen the called partyfhangs 11p-'relay D? re-f leases; and at contact D2 lightsv the lamp LP tox give calledi subscriberYV holdl supervision- -Wherr the. callingparty hangs-up,` relay A; releases`- and" shorts-circuits relay-"B'Which thus falls awayafterx its. slow period. Thereuponfat contacts-.IEP it' remates .earth from` the P" condi-actorV `-andfalsct opensf the. holding circuit forI Vrelay whichi thereupon releases; Relays Cl andiCRiwere also" momentarily operatedf as .previously described? but. without useful. eiect.: The. release foff relay- RS on; the release of relay yconfipletes a`fcircuit at. contacts: RSlt for` restoring theswitch; .to-non Inaiwhereuporr contacts. N2 opengv toiremoye ther guarding earth; from. thee B conductor andi thei equipment. isthena readya for: seizureffon another. connection. v

Similar remarks' apply as:` regards'zvthe locali numbers commencing with'. the.L digits` 721 in whichi casethe.u iirst. digit. is absorbed andi. the; secondad-igit steps: the D; Si R; to level' 2 after Whi'chit' hunts for a. free local thirdA selectorx. Eurther diailed digitsy eiect ther settingoi addition@ switchesin; the: sateliite exchanges the;` iinrst two'J digitsfdialled. are 7.1, this infdicates local numbers requiringV both. met. and second-digit absorption. In. this case'. theV iirstv digit 'Il will be received as justdescribedV and.. re.- laylsfiA,Bf,. JCand` MD will remain ope-:ratedy at, the endof. the train While the discriminating. relay group of Fig. 3, relays DA and OA. willbe. operated; Inresponse. to the second. digit. 1,.the switch. wipers: wil-1 be raisedtothe rst level4 and earthiwillbe applied to lead LSW duringthe slow releaser time?` of relayy CR. In. thesev circum. stances-a. circuit is: completed. for yrelay DB'v which. l-ozcl'cs. up t lead'l LH land the. operating earth is; also extended over lead LZ to restore the D S. R.. to normali In. these circumstances relay JG. is: held as`v lieforevoyer.` its. lower Winding and; owing tothe; connection of earthto lead when offnornia-l. contaci'is` Nit again close, relay 0B;V in. Fig; 3l is operated, and also"y locks` up to lead It ar-.local call.r is. being. completed',I therthird. digit will be 4, 5, 6 or 7 and the D. S. R.` will step cor respondingly'. In* any.l of..these cases` theA effect will bethat: the earth on the lead.. LSW is exe tended.- to lead LLD `to operate relay LD with theresults previously described.

In case-lthehiirsttwo digits dialled are '7.2L or '75,` the'ii'rst digit wi-lllbe absorbedin'. the1usual mananer leavingjr'el'ays B, JG, M3111 and J operated; Infresponse'- tothe dialling of the second digit' 395 4 or5' which characterises a main exchangecall..

it will? be seen from `Fig. 3`1'tha-t the.. application of earth' te lead- LSW is without eiect.4 AConseAb quentl-y'when 'relayvr CR releasesy the holdingfcin cuit for relay .IG-is opened and' it.. also.. releases s0 that' no` further operatienof'magnetVM is1pos sible andthe call is set up over the' main: exe

change;

In" response to-` the dialling Aof a first digitl 0 characteristic of a call to the main exchangemanual board, the-earth from lead LSW is eX- tended`V overtlres'equipment ofI Fig. 3 toleadiLLDA to operate' relay LD: Consequently the Di Si.l nowihunts" over the'tenth level rfrom which err-- tend higlfrgraded trunks totheinain exchange manualboard'. `vEn thiscase the initial connection extending,v over the junction hunter-f toi the trunks normally' used is released.'

`Cmi'sidering now thecase in- 'which the first digit dialled is 8', this characterises amulti-fee call Whichis routed: through themain exchange.

:free multimetering, fee determining equipment connected (to an outleton this level.. The hunting. operation takes place as previously described" and' when ajiree outlet is reached, relay H' ree leases tofstopthe hunting operation at. contacts Sincefl'elay LD is. not operated. in this. in

stance, howeverfthe.connection.to the mainfexchange is maintained and also at contacts HI` theA negativewiper. oivtheDLSg. R. isconnectedto4 the; upper winding of the. spare code relay SC while. atcontacts- H3r thepositive wiper is connected. to the impulsing contactsofV relay A.by way of con- Further impulses dialled are repeated by` contactsAZ Ato the mainiexchangeto set. theswitches therein andarealsorepeated by; contacts Ail over the positive wiper of the D. S." R; to operate the multi-metering equipment which has been taken into use. When the `connection has been fully set up and the wanted party replies, relay D is operated in the usual manner to `release relay MD at contacts D2, `while at contacts `DI the oonnection of battery through the winding of relay SC to the negative wiper of the D. S. R. is shortly replaced by earth over contacts MD to signal to the multi-metering equipment that the D. S. R. is awaiting reception of `the appropriate meter pulse. The release of contacts MDS connects the positive wiper of the D. S. R. to the r metering lead M and the pulses then sent back from the multi-metering equipment thus effect suitable operation of the calling partys meter. During the sending out of the metering pulses, the multi-metering equipment connects earth 'to the P lead to maintain relay RS after the release of relay J which is de-energised by relay MD. This earth is removed when impulse transmission is completed whereupon relay RS releases and the multi-metering equipment is freed for `further use. The Dl S. R. is restored to normal when relay `ireleases at the end of the conversation.

If a spare code is dialled into the multi-meteringV equipment, it is arranged that earth is applied to the negativeleadand this operates relay SC over its upper winding. This relay thereupon locks up over its lower winding at contacts SC4, at contacts SC2 connects number unobtainable tone from lead l2 jto the left-hand winding of relay I whence it is transmitted to the calling party, at contacts SC3releases relay `J whereupon relay RS is released andthe multi-metering equipment is freed, `and at ycontacts SCI opens the loop to themain exchange so that the .0perated switches therein are restored. The opening of` the outgoing` loop releases relay Iwhich bringsdown relay MD and owing to the operation ci relay SC, relayMD releases relay K. The wipers of the D; S. R. are vthen restored to normal but'relaysA, B and SC remainoperated until the callingparty hangs up. 'r r l Relay SC will also be operated if the calling party` dials while the switch JH is still hunting for `a `junction to the main exchange. In this case relay K is not operated and on the operation of relay CR a circuit is completed for relaySC from earth by way of contactsBI, `RS3, CRI and K1. Relay SC then transmits N. U. tone to the subscriber and prevents the 4setting up of a call to aI wrong number owing` to the mutilation of thenrst train i impulses; l

' Considering nowthegeneral operation ofthe r discriminating relays of Fig. 3, with the proposed numbering scheme the following discrimination and absorption facilities after lirst, second and `third digits are requiredasindicated inbriefer form in Fig. 6.`

The facilities available from the various crosslated in Fig. 7.

Considering now the dialling of a main exchange characteristic first digit l, the earth applied to lead LSWA will extend via terminal TZ, l

vertical bank `terminal I, vertical wiper and terminal 2| toV terminal TG whence it extends to terminal TJ which is unwired in the present example. Hence no earth will be returned to the selector over any of the signalling leads and relay JG will release at the end of the digitso as to initiate main exchange call conditions as already described.

Similarly in response to the dialling, of any one of the first digits 2-6 or 9, no earth will be returned to the selector aswill be evident from examination of each of the vertical wiper positions concerned.

If the rst digit dialled is 7, earth on leadl LSW will bring up relay DA via terminals TZ and TF, and at the same time will extend via these terminals to leadv LZ. RelayDA in operating locksto lead LH (earthed from the selector), maintains earth from lead LH on lead IZ, prepares for the reception of a second digit and prepares a circuit for relay OA. The earth on lead LZ initiates release of the selector and when this has taken place earth is applied from the selector to lead LN so as to bring uprelay lOA which locks tolead LH, disconnects the earth to lead LZ and prepares for the second digit.

If the second digit dialled is `3, on the re-:application of earth to lead LSW this will extend via terminals TX and TA to lead LLD so as `to cause the selector to switch overland function as a second selector and so to hunt for a subsequent switch. Similar remarks apply if the second digit dialled is`2.

If the second digit dialled is 1, the earth on lead LSW-will be extended via terminals TZ and TG to bring up relay DB and at the same time it will be fed back over lead LZ so as again to release the selector. Relay DB in operating locks and maintains earth on lead LZ, prepares for the receptionof the third digit and prepares a circuit for relay OB vwhich operates when the selector restores to normal. l

In response to thedialling of a third digit4-7, the earth on lead LSW will be extended backto lead LLD so asto effect discrimination in favour of a local connection.

l In case the rst two digits dialled are 74 or 75, the selector will absorb the rst digit as described, relays DA and OA being operated, while in response to the second digit 4 or 5, the earth on lead LSW is without further effect either on the discriminatingrelaysor as regards feeding back to the selector so that discrimination in favour of a junction call is effected.

In response to the dialling of the iirst digit 0, the earth on lead LSW extends via terminals TZ and TB to lead LLD so as to give local discrimination. r n

In case the rst digit dialled is 8, the `earth on lead LSW extends via terminals TZ and TE to lead LMF so as to cause the selector to cut in and hunt for a multi-fee metering equipment in the manner already described.

From the` above remarks it will be seen that of `the digits which produce actuation of the selector, all the single digits 1-0 have been accounted fOl, but as regards the double digits, digits 70,' 76, 77, 78 land '19` have yet to be dealt with. These digits are not provided for in the numbering 9. In a telephone system, a discriminating selector comprising a two motion switch having a wiper operated on the primary movement thereof in response to series of impulses representing digits transmitted over a calling line connected thereto, a relay group comprising a pair of relays for each digit order which may be absorbed, and a, cross connecting frame for connecting said relay group to said switch through said wiper so as to operate the relay group in accordance with the setting of the Wiper in response to received impulses to either `release the switch or initiate the automatic secondary movement thereof, one relay of said pair operated only in response to the dialling of particular digits of the corresponding order to release said switch, and the other relay of the pair operated in response to the restoration of the switch.

REGINALD TAYLOR.

GEORGE THOMAS BAKER. 20

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

